An implementation of co-ordinate conversion for England, Wales, and
Scotland based on formulae and data published by the Ordnance Survey of
Great Britain.

These modules convert accurately between coordinates given in latitude
and longitude and the OSGB national grid reference system (as used for
maps of England, Wales, and Scotland).

This code is fine tuned to the British national grid system. It is of
no use outside Britain. In fact it's only really useful in the areas
covered by the OS's main series of maps, which excludes the Channel
Islands and Northern Ireland.
